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Regarding infrared photography, I'm quite confused about what wavelengths the colours will represent after the infrared filter was removed from the camera.

How do I find out how to interprete the colours captured by an infrared-converted camera, both in general and, if that's possible, for a specific camera model?

Here are my thoughts:

I know that the purpose of the pre-installed infrared filter is to block wavelengths of ~700+ nm so that the Bayer filter can be thinner. That also means that the pixels of the Bayer filter are actually somewhat sensitive for infrared wavelengths and depend on the infrared filter to block out infrared light.

From this question and from this diagram I deduce the following:

  1. The red channel captures mainly red light, but also a great portion of infrared light.
  2. The blue and green channels also capture infrared light, but much less than the red channel.
  3. It is not possible to distinguish the infrared wavelengths from the red, green and blue ones because neither of those channels distinguishes between its intended wavelength and infrared, because all wavelengths the channel is sensitive to equally factor into the intensity.
  4. Therefore, it is not possible to extract or seperate the infrared intensity from red/green/blue intensities.
  5. (Therefore, it is also not possible to replicate remote-sensing techniques used in remote sensing [e.g. NDVI], meaning that infrared photography is “only” an art form.)

(Please note that I just assume a Bayer filter as it's the most widely one used in consumer electronics, as far as I know.)

Thank you!

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  • For a stationary scene, e.g., some landscapes, make a *four-color- image using an IR-pass filter in addition to IR + visible unfiltered image. The image can then be interpreted through software. Otherwise, as you state, IR + visible imaging is used mainly for art, or for capture of as much light as possible (e.g., night wildlife photography or astrophotography, disregarding true colors). – DrMoishe Pippik Feb 08 '23 at 02:24
  • Have you read any of our existing questions with the [infrared] tag? What did you find? What do they not explain satisfactorily? – Michael C Feb 08 '23 at 02:57

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